Clamping device for clamping printing plates of printing machines



3,119,331 NTING PLATES Jan. 28, 1964 Fig.3

' 0F PRINTING MACHINES Filed Aug. 1, 1962 W. KOCH ETAL CLAMFING DEVICE FOR CLAMPING FRI S r e#m N- WW m HMW a a Nam RE %mun F GY m8 6 United States Patent 3,119,331 CLAMPENG DEVIQE FGR CLAMPING PRENTKNG PLATES 0F PRINTING MACmES Werner Koch and Siegfried Schulnnann, Ofienbach (Main), Germany, assignors to Roland Offsetmaschinenfabrik Faber & Schleieher AG, Olfenbach (Main), Germany, a corporation of Germany Filed Aug. 1, 1962, Ser. No. 214,032 Claims priority, application Germany Aug. 10, 1961 Claims. (Cl. fill-415.1)

The present invention relates to a clamping device for clamping a flexible printing plate in the plate-tensioning rail of a printing machine and, more particularly to a clamping device in which a clamping member is movably disposed in a lengthwise slot of the rail.

There are lmown clamping devices of the general kind peoro; one SIQHOI fiurdurep uonpn In 01 psiiepi eAoqe into the angle defined by two clamping surfaces in the rail, thereby clamping the plate between the rollers and the clamping surfaces. Clamping devices of this kind effect a sufficiently forceful clamping of the plate only when the wedging angle defined by the two clamping surfaces is so small that the specific pressure at the areas of contact between the rollers and the plate is in excess of the limit of elasticity of the plate material so that the rollers are pressed markedly into the surface of the plate. In such event the plate is adequately clamped but it is difiicult to release the clamping rollers from the plate by relaxing the spring pressure supplying the clamping force. It is generally necessary to apply heavy blows to the rollers by suitable tools and the application of such blows can be conveniently applied only when the clamping rollers are accessible from the outside of the machine, which frequently is not the case with modern compact printing machines.

It is a broad object of the invention to provide a clamping device of the general kind above referred to which assures a secure clamping of the printing plate in the tensioning rail of the printing machine and which can be conveniently released without requiring special tools or space which is frequently not available.

A more specific object of the invention is to provide a clamping device of the general kind above referred to in which the clamping member is selectively movable into and out of its clamping position by power-operated means.

Another more specific object of the invention is to provide a clamping device of the general kind above referred to in which movement of the clamping member into or out of the clamping position is effected by a servo system including a hydraulically or pneumatically operated, double-acting piston coacting with the clamping member. Such system affords the advantage that the required powerful clamping or release forces can be obtained with comparatively small components that can be easily accommodated in the limited space available in a modern heavy duty printing machine.

Still another more specific object of the invention is to provide a novel and improved clamping device of the general kind above referred to in which the poweroperated means move through a predetermined idling distance before coacting with the clamping member. As a result kinetic energy is stored in the power-operated means whereby said means impact upon the clamping member with a heavy blow. This has the advantage that the clamping pressure required for the clamping operation is substantially reduced and for the release operation the clamping member is safely loosened from the plate.

A further object of the invention is to provide a novel and improved clamping device in which a pressure medium is supplied to the power-operated means under the control of valve means which release the feed of the pressure medium only after the elfective pressure thereof is fully built up, thereby attaining a maximum force of impact upon the clamping member by the power-operated means.

A still further object of the invention is to provide a novel and improved clamping device of the general kind above referred to in which the clamping member is generally wedge-shaped and is guided transverse of its longitudinal axis in a correspondingly shaped slot of the rail, and an anti-friction bearing is interposed between the clamping member and the rail. As a result a safe guidance of the clamping member at minimum friction is attained.

Other and further objects, features and advantages of the invention will be pointed out hereinafter and set forth in the appended claims constituting part of the application.

In the accompanying drawing a preferred embodiment of the invention is shown by way of illustration and not by way of limitation.

In the drawing:

FIG. 1 is a sectional view of the clamping device according to the invention.

FIG. 2 is a plan view of FIG. 1, and

FIG. 3 is a front elevational view, partly in section.

Referring now to the figures in detail, there is shown a plate-tensioning rail 1 which should be visualized as being movably guided in a conventional manner in the gap of a plate cylinder of a printing machine and which can be displaced in the gap by suitable means such as screws (not shown) to effect tensioning of the printing plate 2. Rail 1 is formed with a lengthwise slot 1a in which is fitted a wedge-shaped or one-sidedly tapered clamping member 3. As is evident, displacement of Wedge 3 towards the left (as seen in FIG. 1) transverse of its longitudinal axis will effect clamping of plate 2 between the respective surfaces of rail 1 and wedge 3, whereas displacement of the wedge towards the right will efiect release of the plate. The wedging angle is so selected that the wedge is self-locking in its clamping position. The surfaces of rail 1 and wedge 3 which engage the end portion of plate 2 to be gripped are preferably roughened to increase the gripping force. In order to reduce the frictional forces that are necessary to release wedge 3 from the plate, anti-friction bearings such as fiat needle bearings 5 are preferably interposed between the slanted surfaces of the wedge and a hardened insert 4 fitted in slot 1a of the rail.

The servo system by means of which the movement of the wedge in either direction is effected, comprises one or several cylinders 6 rigidly secured to rail 1 by any suitable means. A plunger 7 supported on a plunger rod 8 is slidable in each cylinder. Rod 8 has a portion 9 of reduced width and of a length in excess of the transverse width of wedge 3, as is clearly shown in FIG. 1. The plunger 7 is operated by means of compressed air supplied through a supply pipe 25, a reversing or changeover valve 26 of conventional design and a pipe 10. However, the pressure air supplied through pipe 10 does not act directly upon plunger 7, but first upon a pre-control auxiliary control means including a twin plunger 12 which is held in its upper'limit position shown in FIG. 3 by the action of a spring 11. The spring is set to yield in response to an air pressure built-up above a predetermined value. Downward movement of plunger 12 uncovers a duct or bore 13 which leads into the space on the righthand side of plunger 7 thereby causing movement of plunger 7 towards the left. During the first part of the stroke the plunger movement has no effect upon the position of wedge 3, but when a shoulder 14 engages the wedge the same is also moved towards the left, that is, into its clamping position.

The aforedescrihed downward movement of plunger 12 also uncovers a bore 15 leading into the space on the left side of plunger 7 and connected through a space '16 between the two parts of twin plunger 12 and a bore 17 with the atmosphere so that air can escape from the left side of plunger 7 during the clamping operation.

A second auxiliary control assembly of the kind just described should be visualized as being disposed in a bore 18. Pressure air is supplied to the second system through pipe 19. The second system serves to move plunger 7 from the right to the left during the release operation in the manner previously described.

As appears from the previous description of the clamping operation, plunger 7, upon completion of the clamping operation, occupies a position in which shoulder 14 abuts against the respective surface of Wedge 3, that is the gap shown in FIG. 1 between shoulder 14 and the wedge is now formed between a head 29 at the end of rod extension 9 and the wedge. A comparatively weak spring 21 may be provided to retain the plunger assembly in the position in which shoulder 14 abuts against the wedge. As a result, head 20 will move through the initial part of the plunger stroke without coacting with wedge thereby storing kinetic energy and striking the wedge with a heavy blow during the last part of the stroke of plunger '7.

As it is now apparent, rod 8 and its extension constitute a transmission means for transmitting the movements of the plunger to the wedge, and shoulder 14 and head 20 in conjunction with the excess length of rod portion constitute an idling means included in the transmission means.

The change-over of the air flow through pipe 25 from pipe to pipe 19 is effected by operating conventional reversing valve 26. Since, as previously explained, wedge 3 is self-locking in the clamping position, the feed of air can be interrupted immediately after the completion of the clamping operation, thereby reducing the air consumption to a minimum.

In the event the printing machine is very wide, wedge 3 may be subdivided into several separate parts each of which is controlled as previously described.

While the invention has been described in detail with respect to a certain now preferred example and embodiment of the invention, it will be understood by those skilled in the art, after understanding the invention, that various changes and modifications may be made without departing from the spirit and scope of the invention, and it is intended therefore to cover all such changes and modifications in the appended claims.

What is claimed as new and desired to be secured by Letters Patent is:

l. A clamping device for releasably clamping a printing plate in a clamping slot of a tensioning rail of a printing machine, said clamping device comprising a clamping member fitted in said clamping slot movable transverse of the length thereof between a plate clampi-ng position and a plate releasing position, and poweroperated means coacting with said clamping member and operable for selectively moving the same into either of one of said positions, said power-operated means comprising a servo system including a closed cylinder, a plunger coacting with the clamping member slidable in said cylinder, and conduit means for supplying a pressure medium to the cylinder at a selected side of the plunger therein to displace the same in the respective direction, and transmission means coupling said plunger with said clamping member, said transmission means including idling means providing for displacement of the plunger through a predetermined distance prior to transmitting the displacement of the plunger to the clamping member.

2. A clamping device according to claim 1 wherein said transmission means comprise a plunger rod mounting said plunger and having a portion slidably extended through said clamping member in the direction of movement theneef, said extended portion of the rod being of a length in excess of the width of the clamping member in said direction and shouldered at both ends to engage the clamping member after movement of said rod portion through a distance corresponding to its excess length.

3. A clamping device according to claim 1 wherein said clamping slot in the rail has a onesidedly tapered cross-sectional configuration and the clamping member has a complementary cross-sectional configuration, and wherein antifriction bearing means are interposed between the adjacent tapered surfaces of the clamping member and the rail.

4. A clamping device for releasably clamping a printing plate in a clamping slot of a tensioning rail of a printing machine, said clamping device comprising a clamping member fitted in said clamping slot and movable transversely of the length thereof between a plate-clamping position and a plate-releasing position, power-operated means coacting with said clamping member and operable for selectively moving the same into either one of said positions, said power-operated means comprising a servo system including a closed cylinder, a plunger meeting with the clamping member slidable in the cylinder, conduit means for supplying a pressure medium to the cylinder on a selected side of the plunger to displace the same in the respective direction, and auxiliary control means controlling the flow of the pressure mediurn to the cylinder, said control means delaying the flow of the pressure medium to the respective side of the plunger to effect a build-up of the pressure of the pressure medium prior to acting upon the plunger and comprising valve means including a plunger closing in one position the flow of pressure medium to the cylinder and opening said flow in another position, and spring means urging the plunger of the valve means into the flow-closing position but yielding for movement of the plunger into its flow-opening position in response to a pressure of the pressure medium above a predetermined value acting upon the plunger of the auxiliary control means.

5 A clamping device according to claim 4 wherein said valve means comprise a cylinder in which said valve plunger is displaceable, said valve cylinder and plunger defining a closed space in said cylinder, a first duct connecting said space to a source of pressure medium and a second duct connecting said space to the cylinder for the plunger coasting with the clamping member, said spring means urging the valve plunger into the position closing the second duct.

References Cited in the file of this patent UNITED STATES PATENTS 2,022,681 Lougee et a1 Dec. 3, 1935 FOREIGN PATENTS 886,311 Germany Aug. 13, 1953 

1. A CLAMPING DEVICE FOR RELEASABLY CLAMPING A PRINTING PLATE IN A CLAMPING SLOT OF A TENSIONING RAIL OF A PRINTING MACHINE, SAID CLAMPING DEVICE COMPRISING A CLAMPING MEMBER FITTED IN SAID CLAMPING SLOT MOVABLE TRANSVERSE OF THE LENGTH THEREOF BETWEEN A PLATE CLAMPING POSITION AND A PLATE RELEASING POSITION, AND POWEROPERATED MEANS COACTING WITH SAID CLAMPING MEMBER AND OPERABLE FOR SELECTIVELY MOVING THE SAME INTO EITHER OF ONE OF SAID POSITIONS, SAID POWER-OPERATED MEANS COMPRISING A SERVO SYSTEM INCLUDING A CLOSED CYLINDER, A PLUNGER COACTING WITH THE CLAMPING MEMBER SLIDABLE IN SAID CYLINDER, AND CONDUIT MEANS FOR SUPPLYING A PRESSURE MEDIUM TO THE CYLINDER AT A SELECTED SIDE OF THE PLUNGER THEREIN TO DISPLACE THE SAME IN THE RESPECTIVE DIRECTION, AND TRANSMISSION MEANS COUPLING SAID PLUNGER WITH SAID CLAMPING MEMBER, SAID TRANSMISSION MEANS INCLUDING IDLING MEANS PROVIDING FOR DISPLACEMENT OF THE PLUNGER THROUGH A PREDETERMINED DISTANCE PRIOR TO TRANSMITTING THE DISPLACEMENT OF THE PLUNGER TO THE CLAMPING MEMBER. 